1. Field of the Invention
The present invention relates generally to the processing of substrates to form integrated circuit wafers and equipment useful for such processing. More particularly, the invention relates to processes and equipment for moving a lifting member within a sealed vacuum chamber.
2. Background of the Related Art
In the fabrication of integrated circuits, the processes are often carried out in a vacuum environment to, among other things, reduce the particulate level to which the wafers are exposed. Robots within the vacuum processing systems move the wafers horizontally through the system and position the wafers in a series of processing stations in which a series of processing steps are carried out.
Within each of the processing stations, or chambers, the wafer is transferred from the robot onto a pedestal. To complete the transfer, the robot, which supports the wafer from the bottom, positions the wafer over the pedestal. A receiver apparatus, typically in the form of a plurality of vertically extending fingers connected at their lower ends on a lifting hoop (although other embodiments are known), moves upward through slots in the pedestal to lift the wafer from the robot. The receiver apparatus has a shaft extending out of the bottom of the chamber where it is connected to a positioning device. With the wafer supported by the receiver apparatus, the robot retracts from the chamber. The processing pedestal then moves upward beyond the receiving apparatus lifting the wafer from the receiver apparatus and into an upper position where the process step is performed. Like the receiving apparatus, the processing pedestal has a shaft extending through the bottom of the chamber where it is driven by a separate positioning device.
In prior art devices, the pedestal shaft is generally concentric with the platform. The lifting hoop of the receiving apparatus is also generally concentric with the platform so that the fingers are equally spaced about the platform to provide sufficient and balanced support for the wafer. However, in the prior art devices, the shaft of the receiving apparatus is offset from the axis of the lifting hoop and is parallel to the processing platform shaft. An extension arm connects the lifting hoop to the receiving apparatus shaft.
Accordingly, the prior art devices have two parallel shafts extending through the bottom of the chamber and require two openings in the bottom of the chamber. Each of these openings must be sealed in order to maintain the required vacuum within the chamber. To seal the chamber around the openings, a collapsible bellows extends between the platform and the chamber bottom and a separate collapsible bellows extends between the upper end of the receiving apparatus shaft and the chamber bottom. The collapsible bellows is required due to the relative movement of the shafts in the chamber. However, each of the vacuum to atmosphere interfaces, the bellows seals, are a source for leaks which result in system inefficiency and downtime.
Also, the prior art designs necessitate the use of a relatively larger chamber because of the offset receiver shaft. This larger chamber takes additional space, a precious commodity in manufacturing clean rooms, and requires additional material to manufacture and additional energy to maintain the required vacuum within the chamber. Having the offset shaft also restricts the use of a circular chamber and increases inefficiency and manufacturing costs.